In secondary analyses, multi-level mixed-effects models will be used to estimate the average individual monthly rate of change in 25(OH)D, compare this rate between dose groups, and explore the effects of covariates on the rate of change. These models include fixed effects for dose group, time, and the group-time interaction, and a random intercept effect, with additional covariate effects as required. Time will be considered a continuous variable, measured in months rather than assuming structured visit occurrences. An unstructured covariance matrix will be assumed. The multi-level modeling approach also will be used to evaluate the longitudinal association between 25(OH)D and the safety parameters calcium, iPTH (log-transformed), phosphorus, and urinary calcium, creatinine, and calcium: creatinine levels. The cumulative occurrence of pregnancy complications such as preterm labor and infection will be compared between dose group levels using logistic regression. All analyses will be performed using SAS (SAS Institute Inc., Cary NC).